1. Field of the Invention
The present invention relates to a oscillation suppression device applied to a small ship or a boat such as a leisure boat, a suspension type transportation machine such as a gondola, a suspension from a helicopter or the like. It also relates to a ship provided with the oscillation suppression device.
2. Description of the Related Art
In a conventional oscillation suppression device for suppressing oscillation of a small ship, such as a leisure boat, a drum brake or a generator is coupled to a gimbal shaft so that an angular velocity of the gimbal may be adjusted by the resistance of the drum brake or the generator.
FIG. 14 shows an arrangement of the conventional oscillation suppression device. A flywheel 1 which constitutes the oscillation suppression device is connected to a flat type spin motor 2 through a spin shaft 9 and is rotated at a high speed (with an angular velocity Q of the flywheel) by the spin motor 2. The flywheel 1 is supported by a gimbal 4 through spin system bearings 3a and 3b so as not to be prevented from rotating at a high speed.
The gimbal 4 has a gimbal shaft 4a and rotates about the gimbal shaft 4a at an angular velocity .theta.. The gimbal shaft 4a is supported by support frames 6a and 6b through gimbal system bearings 5a and 5b so that the gimbal 4 is not prevented from rotating. Further, each support frame 6a, 6b is fixed to an object 10 in which oscillation is to be suppressed by the oscillation suppression device. The support frames 6a and 6b transmit a gyro torque T.psi. generated by the rotation of the gimbal 4 to the object to be controlled for reducing the oscillation angular velocity .PHI. of the object to be controlled.
A drum brake 7 or a generator 8 is connected to one end of the gimbal shaft 4a. The angular velocity .theta. of the gimbal is controlled by the resistance of the drum brake 7 or the generator 8. Thus, the gyro torque T.psi. is controlled and the oscillation angular velocity .PHI. of the object to be controlled is reduced. As shown in FIG. 15, the drum brake 7 is provided on the gimbal shaft 4a of a control moment gyro so that the angular velocity .theta. of the gimbal 4 is controlled by the frictional force of the drum brake 7.
In the case where the drum brake 7 is used for controlling the angular velocity .theta. of the gimbal 4, the brake torque to be applied to the gimbal shaft 4a may be kept constant. For this reason, it is impossible to finely control the oscillation relative to the oscillation angular velocity .PHI. of the object to be controlled. Also, since a frequency band of oscillation for the object to be controlled is narrow, it is impossible to apply this system to objects where the amplitude of the oscillations is large.
Also, if the drum brake 7 is used, it is difficult to remove dust, moisture or the like adhered to a surface of the drum brake 7, and the heat radiation from the frictional surface is not satisfactory. Accordingly, it is difficult to properly maintain the drum brake, which results in deteriorating performance.
On the other hand, in the case where the generator 8 is used to control the rotation of the gimbal shaft 4a, a load resistor having a predetermined resistor value is connected to a terminal of the generator 8 to be connected to the gimbal shaft 4a to impart a brake force to the rotation of the gimbal shaft 4a to thereby control the angular velocity .theta. of the gimbal 4 as disclosed in Japanese Patent Application Laid-Open No. Hei 6-129484 filed by the present applicants and entitled "Rotary Oscillation Suppressing Device". However, since the resistor value of the resistor provided in the generator 8 is kept constant, the same problem would be encountered as in the case of the brake drum 7.